Among the processes governing the energy balance in the mesosphere and lower
thermosphere (MLT), the quenching of CO<sub>2</sub>(&nu;<sub>2</sub>) vibrational
levels by collisions with O atoms plays an important role. However, there is
a factor of 3–4 discrepancy between the laboratory measurements of the
CO<sub>2</sub>-O quenching rate coefficient, <i>k</i><sub>VT</sub>, and its value estimated
from the atmospheric observations. In this study, we retrieve <i>k</i><sub>VT</sub> in
the altitude region 85–105 km from the coincident SABER/TIMED and Fort
Collins sodium lidar observations by minimizing the difference between
measured and simulated broadband limb 15 μm radiation. The averaged
<i>k</i><sub>VT</sub> value obtained in this work is 6.5 &plusmn; 1.5 &times; 10<sup>&minus;12</sup> cm<sup>3</sup> s<sup>−1</sup>
that is close to other estimates of this
coefficient from the atmospheric observations. However, the retrieved
<i>k</i><sub>VT</sub> also shows altitude dependence and varies from
5.5 &plusmn; 1.1 &times; 10<sup>&minus;12</sup> cm<sup>3</sup> s<sup>−1</sup> at 90 km to
7.9 &plusmn; 1.2 &times; 10<sup>&minus;12</sup> cm<sup>3</sup> s<sup>−1</sup> at 105 km. Obtained results
demonstrate the deficiency in current non-LTE modeling of the atmospheric 15
μm radiation, based on the application of the CO<sub>2</sub>-O quenching and
excitation rates, which are linked by the detailed balance relation. We
discuss the possible model improvements, among them accounting for the
interaction of the "non-thermal" oxygen atoms with CO<sub>2</sub> molecules.